2020-06-30 05:54:34 +01:00
|
|
|
// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
|
|
|
|
// Use of this source code is governed by a BSD-style
|
|
|
|
// license that can be found in the LICENSE file.
|
|
|
|
|
|
|
|
// Package disco contains the discovery message types.
|
|
|
|
//
|
|
|
|
// A discovery message is:
|
|
|
|
//
|
|
|
|
// Header:
|
|
|
|
// magic [6]byte // “TS💬” (0x54 53 f0 9f 92 ac)
|
|
|
|
// senderDiscoPub [32]byte // nacl public key
|
|
|
|
// nonce [24]byte
|
|
|
|
//
|
|
|
|
// The recipient then decrypts the bytes following (the nacl secretbox)
|
|
|
|
// and then the inner payload structure is:
|
|
|
|
//
|
|
|
|
// messageType byte (the MessageType constants below)
|
|
|
|
// messageVersion byte (0 for now; but always ignore bytes at the end)
|
|
|
|
// message-paylod [...]byte
|
|
|
|
package disco
|
|
|
|
|
|
|
|
import (
|
|
|
|
"encoding/binary"
|
|
|
|
"errors"
|
|
|
|
"fmt"
|
|
|
|
"net"
|
|
|
|
|
|
|
|
"inet.af/netaddr"
|
|
|
|
)
|
|
|
|
|
2020-07-01 20:56:17 +01:00
|
|
|
// Magic is the 6 byte header of all discovery messages.
|
|
|
|
const Magic = "TS💬" // 6 bytes: 0x54 53 f0 9f 92 ac
|
|
|
|
|
|
|
|
// NonceLen is the length of the nonces used by nacl secretboxes.
|
|
|
|
const NonceLen = 24
|
|
|
|
|
2020-06-30 05:54:34 +01:00
|
|
|
type MessageType byte
|
|
|
|
|
|
|
|
const (
|
|
|
|
TypePing = MessageType(0x01)
|
|
|
|
TypePong = MessageType(0x02)
|
|
|
|
TypeCallMeMaybe = MessageType(0x03)
|
|
|
|
)
|
|
|
|
|
|
|
|
const v0 = byte(0)
|
|
|
|
|
|
|
|
var errShort = errors.New("short message")
|
|
|
|
|
|
|
|
// Parse parses the encrypted part of the message from inside the
|
|
|
|
// nacl secretbox.
|
|
|
|
func Parse(p []byte) (Message, error) {
|
|
|
|
if len(p) < 2 {
|
|
|
|
return nil, errShort
|
|
|
|
}
|
|
|
|
t, ver, p := MessageType(p[0]), p[1], p[2:]
|
|
|
|
switch t {
|
|
|
|
case TypePing:
|
|
|
|
return parsePing(ver, p)
|
|
|
|
case TypePong:
|
|
|
|
return parsePong(ver, p)
|
|
|
|
case TypeCallMeMaybe:
|
|
|
|
return CallMeMaybe{}, nil
|
|
|
|
default:
|
|
|
|
return nil, fmt.Errorf("unknown message type 0x%02x", byte(t))
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
// Message a discovery message.
|
|
|
|
type Message interface {
|
|
|
|
// AppendMarshal appends the message's marshaled representation.
|
|
|
|
AppendMarshal([]byte) []byte
|
|
|
|
}
|
|
|
|
|
|
|
|
// appendMsgHeader appends two bytes (for t and ver) and then also
|
|
|
|
// dataLen bytes to b, returning the appended slice in all. The
|
|
|
|
// returned data slice is a subslice of all with just dataLen bytes of
|
|
|
|
// where the caller will fill in the data.
|
|
|
|
func appendMsgHeader(b []byte, t MessageType, ver uint8, dataLen int) (all, data []byte) {
|
|
|
|
// TODO: optimize this?
|
|
|
|
all = append(b, make([]byte, dataLen+2)...)
|
|
|
|
all[len(b)] = byte(t)
|
|
|
|
all[len(b)+1] = ver
|
|
|
|
data = all[len(b)+2:]
|
|
|
|
return
|
|
|
|
}
|
|
|
|
|
|
|
|
type Ping struct {
|
|
|
|
TxID [12]byte
|
|
|
|
}
|
|
|
|
|
|
|
|
func (m *Ping) AppendMarshal(b []byte) []byte {
|
|
|
|
ret, d := appendMsgHeader(b, TypePing, v0, 12)
|
|
|
|
copy(d, m.TxID[:])
|
|
|
|
return ret
|
|
|
|
}
|
|
|
|
|
|
|
|
func parsePing(ver uint8, p []byte) (m *Ping, err error) {
|
|
|
|
if len(p) < 12 {
|
|
|
|
return nil, errShort
|
|
|
|
}
|
|
|
|
m = new(Ping)
|
|
|
|
copy(m.TxID[:], p)
|
|
|
|
return m, nil
|
|
|
|
}
|
|
|
|
|
|
|
|
// CallMeMaybe is a message sent only over DERP to request that the recipient try
|
|
|
|
// to open up a magicsock path back to the sender.
|
|
|
|
//
|
|
|
|
// The sender should've already sent UDP packets to the peer to open
|
|
|
|
// up the stateful firewall mappings inbound.
|
|
|
|
//
|
|
|
|
// The recipient may choose to not open a path back, if it's already
|
|
|
|
// happy with its path. But usually it will.
|
|
|
|
type CallMeMaybe struct{}
|
|
|
|
|
|
|
|
func (CallMeMaybe) AppendMarshal(b []byte) []byte {
|
|
|
|
ret, _ := appendMsgHeader(b, TypeCallMeMaybe, v0, 0)
|
|
|
|
return ret
|
|
|
|
}
|
|
|
|
|
|
|
|
// Pong is a response a Ping.
|
|
|
|
//
|
|
|
|
// It includes the sender's source IP + port, so it's effectively a
|
|
|
|
// STUN response.
|
|
|
|
type Pong struct {
|
|
|
|
TxID [12]byte
|
|
|
|
Src netaddr.IPPort // 18 bytes (16+2) on the wire; v4-mapped ipv6 for IPv4
|
|
|
|
}
|
|
|
|
|
|
|
|
const pongLen = 12 + 16 + 2
|
|
|
|
|
|
|
|
func (m *Pong) AppendMarshal(b []byte) []byte {
|
|
|
|
ret, d := appendMsgHeader(b, TypePong, v0, pongLen)
|
|
|
|
d = d[copy(d, m.TxID[:]):]
|
|
|
|
ip16 := m.Src.IP.As16()
|
|
|
|
d = d[copy(d, ip16[:]):]
|
|
|
|
binary.BigEndian.PutUint16(d, m.Src.Port)
|
|
|
|
return ret
|
|
|
|
}
|
|
|
|
|
|
|
|
func parsePong(ver uint8, p []byte) (m *Pong, err error) {
|
|
|
|
if len(p) < pongLen {
|
|
|
|
return nil, errShort
|
|
|
|
}
|
|
|
|
m = new(Pong)
|
|
|
|
copy(m.TxID[:], p)
|
|
|
|
p = p[12:]
|
|
|
|
|
|
|
|
m.Src.IP, _ = netaddr.FromStdIP(net.IP(p[:16]))
|
|
|
|
p = p[16:]
|
|
|
|
|
|
|
|
m.Src.Port = binary.BigEndian.Uint16(p)
|
|
|
|
return m, nil
|
|
|
|
}
|
2020-07-02 18:48:13 +01:00
|
|
|
|
|
|
|
// MessageSummary returns a short summary of m for logging purposes.
|
|
|
|
func MessageSummary(m Message) string {
|
|
|
|
switch m := m.(type) {
|
|
|
|
case *Ping:
|
|
|
|
return fmt.Sprintf("ping tx=%x", m.TxID)
|
|
|
|
case *Pong:
|
|
|
|
return fmt.Sprintf("pong tx=%x", m.TxID)
|
|
|
|
case CallMeMaybe:
|
2020-07-02 18:52:23 +01:00
|
|
|
return "call-me-maybe"
|
2020-07-02 18:48:13 +01:00
|
|
|
default:
|
|
|
|
return fmt.Sprintf("%#v", m)
|
|
|
|
}
|
|
|
|
}
|